WASHINGTON  In an attempt to increase domestic production of alternative fuel sources, the Bush administration has proposed allowing ethanol plants to send more hazardous air pollutants into the air.

The Environmental Protection Agency announced Wednesday that it has proposed a rule that would raise the emissions threshold for corn milling plants that produce ethanol fuel, allowing those plants to emit up to 250 tons per year of air pollutants before triggering tougher restrictions on production.

Sen. John Thune, R-S.D., has been pushing the agency to make the change since last fall, noting that corn milling plants that produce ethanol products for human consumption had a higher emissions threshold than those that produce ethanol fuel.

The change, he says, will help the country navigate gasoline price spikes by producing more renewable energy.

The plants "are poised to produce ethanol at higher capacities, and farmers are prepared to grow and sell more corn," Thune said.

President Bush pushed increased production of renewable fuels in his State of the Union speech this year, urging Congress to spend federal dollars on ethanol research in order to free the country of its "addiction" to foreign oil.

Though environmentalists have generally supported increased use of ethanol and other renewable fuels, some point out that the EPA has settled several noncompliance cases with companies producing ethanol fuel. In several of the cases, the agency noted that the plants "burn off gases which emit volatile organic compounds and carbon monoxide into the air."

Frank O'Donnell, director of the environmental advocacy group Clean Air Watch, said the rule could "create a new problem by trying to solve an old problem."

"This appears to be an attempt to cut a break for some ethanol producers," he said. "My concern is that this could lead to more pollution in communities near the refineries."